Protective device for series transformers.



PATENTED AUG. 18, 1907.

PROTECTIVE DEVICE POE. 313E153 TRANSFORMERS.

APPLIGATIOH FILED NOV, 12,1904.

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PRGTEOTIVE DEVICE APEL'JIUATIOXI FILED HG'?.12.1904.

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CHARLES EVELETH. OF SGi-llWEC'lAlYY, NEW YORK, ASSIGYOR 'lO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YOR h PROTECTI E DEVIQE FOR SERIES TRANSFORMERS.

Specification. of Let-tors Patent Patented Aug. 13, on.

Application filed November 12,1904. sum in. 232,463.

To all whozuii may. concern:

Be it known that I. CHARLES E. Eynnrrrrr a citizen of the Unite States, residing at Schenectady, county of Scheuecnuly, Suite-of New York, have invented certain new and useful Improvements in Protective Devices f u Series Transformers, of which the following is o, specification.

in electrical systems of the constant current type it is common to insert 9. series transformer in the main circuit and thus supply a local circuit with constant current of a higher or lower value than that in the main e :cuit. This arrangement is porticulm'ly useful when the load consists of a mixture of arc and incandescent lumps, and is rendered necessary by the difference in the eurrent-currying capacity of such lamps as commonly nmnufuctured. Incandescent lamps adopted for use on series circuits are operated on approxi- 1 tely one and pne half umperes, whereas arc liuups rquiresnyseveii and one half. Some systemoi trimsformutioh is therefore necessary when a mixed load is curried. 'This transformation may be produced by transform er having its-primary connected in series with the main circuit and its secondary supplying constant current to the local circuit. As the secondary oi the transformer normally operates on elo d circuit the primary affords substantially no mpei "we to the main line current under normal conditions oi working, but

' euson the secondary circuit is open the de- M ing action of the secondary current on the transformer core will no longer be present and the trains- .i'orruer nury will act on a powerful reactive coil to the main line current.

It is the object of this inventioirto provide a means whereby no detrimental reactive effect will be produced by the series tmnsformer when the local circuit is opened. or when for any reason the secondary current decreases abnormally in value.

Figure l is u diagrammatic reprcsenhition of one spe ci s oi my invention in which n short-c1rcuiting switch is provided for uutiunulicailly sluu't('ircuili1ig the priimu'y of thitransformer when the voltage across the primary rein-hes an abnormal value because of the fuiluro of curren n the local circuit; F :2 shows a. short oircuiting switch for n s ries transformer controlled di re -tly by the current in the local circuit: Fig. 3 shows it switch which uutomulicully short circuits a portion of the secoiuh winding of th e series l1;J.iiSiO1l1lLl' thus producing a loi'irlcireuit through the shortwircuited turns of such value us to prove: on uhuornntl leiicinncv oi the prinutry on the Inu-iu circuit; F g. 4 shows on ningenu-ut in which the low-oi short circuit produced by thibreuk down of u- [ihn cutout of ordinary form shunted ucross 2L portion of the primary winding.

'lhrougliout all the drawings the some refcremre nuineruls apply to similur parts.

The series lumps 1 or other constant current translating devices are Operated by current from at constant current source 2, such as n movable coil tnuisformer or constant current dynamo of ordinary iorn'r. In series with these lights is or primary 3 of u constant current transformer for supplying a local circuit through arc lumps 4, or other aniluhle translating devices having a. current carrying capacity different from that of the lamps 1.

When normal current is flowing through the arc lamps 4 and through the secondary 5 of the series tmnsformer the reactauce offered by the primary 3 to the current in the main circuit is comparatively small, but on the other hand if for any reason the local circuit through the are lumps is opened, as by failure of one of the lamps, the primary 3 will operate as a powerful react-once in the main circuit and thus cut down the current in the main circuit to such awnlue as to make the operation of-the series lamps unsiitisfuctory. To overcome this difficulty I provide an automatic means for either short-circuiting the primary winding of the transformer, or for establishing a local current in one of the transformer windings 0i sufiicicnt miners practically remove the reactive power of the transl'onner. In Fig. l the primary winding is provided witlra top 6 and electromagnet 7 is connected between this top and one end of the primary. This electromagnet is provided with a movable armature 8, the lower end of which is normally held at some distance from the core oi the electromu'gnet 7 by eoilspring 9. A horizontal tripping bar 10 is pivoted to the upper end of armature 8 and" serves as a trigger for a vertically moying plunger 11. This plunger carries at its lower end a metallic cross piece 12 which serves as a switch to electrically connect two terminalrriilend 14 connected to the respective ends of the primary winding. A coil spring 15 encircling the plunger 11 serves to finnly seat the switch 12 l on these terminals 18 and 14 when the tripping bar 10 is withdrawn by the action of armature 8. The winding of the electromagnet 7 is so proportioned with respect LO til? strength of coil spring 9 and the voltage supplied from the transformer tap that under normal conditions of operation the attractive power of the electromagnet is not suilicient to overcome the moment exerted by the coil spring 9 and the tripping bar and plunger remain in the position shown. If however one of the lamps in the local circuit becomes accidentally open-circuited, or if for any reason the local current decreases abnormally in vulue, the voltage across the primary 3 will immediately increase and the increased current in electromagnet 7 will be suilicient to attract the armature 8 and withdraw the tripping bur 10, and thus permanently short-circuit the primary winding and so prevent an abnormal decrease in the main line current.

In Fig. 2 a solenoid 1G is connected in series with the and 'One end of the secondary is made extra heavy and 1 capable oi carrying continuously a heavy local current.

' The tripping electromagnet and the short-circuiting plunger are in all respects similar to those shown in Fig. l and the operation is the same, except that instead of short'circuiting the transformer primary, the short circuit is across a few turns of the secondary winding, thus 1 producing a heavy local current through these turns and permitting the passage of enough current throngh this local circuit to prevent an abnormal increase in reactance in the transformer primary.

In Fig. 4 a tap 18 is provided for the primary winding 2 and a film cut-out of ordinary form is connected between this tap and one end of the winding so that upon abnormal increase in voltage, as by failure of the current in the local circuit, the film cut-out will be broken down and a local short circuit produced through the heavy transformer turns shunted by the film cut-out,

thus preventing an abnormal increase in the reactive effect of the primary. It is obvious that this film cutout might be inserted across a portion of the secondary winding, if such an arrangement appeared desirable,

but by using it across a portion of the primary the increase in cross section oi'the winding to secure ample current carrying capacity for the local current is considerably less than would otherwise be necessary. If desired the film eutout may be used in Fig. 1 in series with the tap 6 to increase the operating voltage of the electromagnet 7, but such a modification I believe to be included within the scope of my invention, as deiined by the appended claims. Although I believe my involution to be particularly valuable when used in connection with a mixed load of arc and incandescent lamps it is obvious that it is applicable to circuits containing a mix d load of constant current apparatus of any description.

What I claim as new and desire to secure by Letters Patent of the United States, is:

g 1 in an electrical system, a plurality of translating devices, means for supplying a substantially constant current thereto. a transformer having its primary winding in series with said devices and its secondary winding con nected to a normally closed local circuit, a tap for one of said windings, and automatic meanswonnected to said tap for preventing an abnormal decrease in the current through said translating devices when the current in said local circuit is interrupted.

2. In an electrical system, a circuit contnining a pinrality of translating devices connected in series, means for supplying a substantially constant current thereto, a

transformer having its primary winding connected in" series with said translating devices and its secondary winding connected to a local circuit, a tap for one of said transformer windings, an electromagnetic device ener gized by current from said tap, and means opermed by said electromagnetic device for automatically sliort-circniting turns of one of said windings when the current in said local circuit is decreased abnormally.

:i. in an electrical system, a constant currentcircuit, a transformer connected thereto, a local circuit supplied by current from said transformer. an electromagnet in shunt with a portion of one of said transformer windings, and means actuated by said eiectromagnet for short-circuitlng said winding when the pressure across said electromngnet reaches a predetermined value.

4. in an electrical system, a circuit containing a plurality of translating devices connected in series, means for supplying a-substantlaliy constant current thereto; a transformer having its primary winding connected in series with said translating devices and its secon'dury winding connected to a local circuit, a tap io'r said primary winding, an eiectromagnet energized by current from suid tap, and means'opersted by said electromagnet for short-circuiting said primary when the voltage across said primary reaches a predetermined value.

in witness whereof I have hereunto set my hand this 7th day of November, 1904.

CHARLES E. EVELETH.

Witnesses BENJAMIN B. H LL, Hanan Onronn. 

